The innovations disclosed herein pertain to retention systems, and more particularly, but not exclusively, to retention systems for electrical batteries, such as, for example, retention systems configured to support a plurality of batteries operatively coupleable with each other. Some disclosed retention systems are configured to reliably support a plurality of batteries in a rotating reference frame, such as, for example, in a rotor of an wind turbine configured to generate electricity.
According to some estimates, the installed base of wind-turbine based electricity generation in the United States has grown from about 2,500 megawatts (MW) at the end of the year 2000 to about 40,200 MW at the end of 2010. During that time frame, a typical wind-turbine efficiency for converting kinetic energy of moving air (or wind) to electrical power has improved, at least in part by the proliferation of wind turbines incorporating adjustable-pitch rotor blades.
FIG. 1A and FIG. 1B illustrate a common horizontal-axis wind turbine 10 mounted atop a tower 20 in an elevated position (e.g., between about 50 meters and about 100 meters above ground level 30, for example, between about 65 meters and about 80 meters). The illustrated wind-turbine 10 has a rotor 15 configured to rotate about a generally horizontal axis of rotation 16. A drivetrain transmits power from the rotor 15 to an electrical generator positioned within a nacelle 17. The rotor 15 has a plurality of blades 18 extending radially outward from a hub shown in more detail in FIG. 1C.
Although a wind turbine 10 can generate electricity while the rotor 15 rotates, if the wind changes direction or stops blowing, the blades 18 may insufficiently urge the rotor in rotation, causing the power generation capability of the wind turbine 10 to drop precipitously. Accordingly, some wind-turbine assemblies of the general type just described (e.g., having a rotor and a drivetrain) are capable of rotating about a vertically oriented axis 21 (e.g., an axis extending longitudinally of the tower 20), enabling the rotor 15 to be positioned facing the wind.
As well, some wind turbines allow the pitch angle of a rotor blade 18 to be set using an electrical motor and drivetrain configured to rotate the blade about a blade axis of rotation, as indicated in FIG. 1C. A pitch angle of each rotor blade 18 relative to a wind direction or vector) can be selected to correspond to, for example, a desired mechanical load on one or more of the blades 18, rotor 15, drivetrain and tower 20. By selecting a desired pitch angle, the rotor's ability to capture energy from the wind can be tuned while simultaneously protecting the turbine 10 and tower 20 from damage that otherwise could occur from high winds.
Some models of wind turbines provide one or more batteries for powering an electrical motor configured to drive a pitch-rotation drivetrain corresponding to a given rotor blade 18. For example, each rotor blade 18 can be configured to receive a respective battery (or array of battery elements electrically coupled with each other) for powering the respective rotor's pitch-rotation drivetrain. Such a battery (or array of battery elements) is sometimes referred to as a “pitch-control battery.”
A conventional pitch-control battery has an array of, for example, six individual battery elements being so electrically couplable with each other (e.g., in series or in parallel) as to be capable of providing desired electrical characteristics suitable for powering an electrical motor and pitch-rotation drivetrain. In conventional retention systems, each of the individual battery elements in the array of battery elements is epoxied or otherwise permanently affixed to a generally planar base rendering the entire array of battery elements inoperable if even one of the battery elements becomes inoperable.
The base, in turn, is configured to be suitably mounted in a rotor blade 18. As the rotor 15 rotates, the base and corresponding array of battery elements of the pitch-control battery orbit the generally horizontal axis of rotation 16, in some instances placing the base and other components under substantial stresses arising from, for example, centripetal acceleration.